CIHM 
Microfiche 
Series 
(IMonographs) 


ICMH 

Collection  de 
microfiches 
(monographies) 


Canadian  Institute  for  Historical  Microroproductions  /  Instttut  Canadian  de  microreproductlons  historiques 


Technical  and  Bibliographic  Notes  /  Notes  techniques  et  bibliographiques 


The  Institute  has  attempted  to  obtain  the  best  original 
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the  Images  in  the  reproduction,  or  which  may 
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jnque 
:culeur 


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intirieure. 

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apparaissent  dans  le  texte,  mais.  lorsque  ceia  ^tait 
possible,  ces  pages  n'ont  pas  M  tilm^es. 


L'Instilut  a  microfilm*  le  meilleur  exemplaire  qu'il  lui  a 
i\k  possible  de  se  procurer.  Les  details  de  cet  exem- 
plaire qui  sont  peut-«tre  unkjues  du  point  de  vue  bibli- 
ographique,  qui  peuvent  modifier  une  image  reproduite, 
ou  qui  peuvent  exiger  une  modification  dans  la  m^tho- 
de  normale  de  filmage  sont  indiquis  ci-dessous. 

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{     I  Showthrough  /  Transparence 

I — I  Quality  of  print  varies  / 


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Comprend  du  materiel  suppl^mentaire 

Pages  wholly  or  partially  obscured  by  errata  slips, 
tissues,  etc.,  have  been  refilmed  to  ensure  the  best 
possible  image  /  Les  pages  totalement  ou 
partiellement  obscurcies  par  un  feuillet  d'errata,  une 
pelure,  etc.,  ont  M  filmies  k  nouveau  de  fa^on  k 
obtenir  la  nf>eilleure  image  possible. 

Opposing  pages  with  varying  colouration  or 
discotourations  are  filmed  twice  to  ensure  the  best 
possible  Image  /  Les  pages  s'opposant  ayant  des 
colorations  variables  ou  des  decolorations  sont 
film^es  deux  fois  afin  d'obtenir  la  meilleure  InriageL 
possible. 


r~7\  Addittonal  comments  / 

ii_J  Commentaires  supplime.ntaires: 


Pagination  is  as  follows:  p.  195-203. 

La  pagination  est  comme  suit:  p.  195-203. 


TMt  Htm  It  filmed  %x  iht  rtduellon  ratio  chtcktd  btlow  / 

C«  doeumtnt  ttt  (ilm4  au  Uus  dt  rMuction  indiqut  ci-dtiieut. 


10x 

14x 

18x 

22x 

26x 

30x 

* 

i4» 

l«tt 

20x 

24  X 

28x 

32x 

Th«  copy  filmad  h«r«  has  iM«n  raproduead  thanks 
to  tha  ganarosity  of: 


L'axamplaira  filmi  fut  raproduit  grAca  i  la 
g4n4rositi  da: 


University  of  Toronto 

Gerstein  Sciences  Information  Centre 

Tha  imagaa  appaaring  hara  ara  tha  bast  quality 
possibia  eonsidaring  tha  condition  and  lagibility 
of  tha  original  copy  and  )n  kaaping  with  tha 
filming  contract  spocif ications. 


University  of  Toronto 

Gerstein  Sciences  Information  Contre 

Las  imagas  suivantas  ont  ttt  raproduitas  svac  la 
plus  grand  soin.  compta  tanu  da  la  condition  at 
do  la  nattat*  da  raxampiaira  film*,  at  tn 
conformity  avac  las  conditions  du  contrat  da 
filmaga. 


Original  capias  in  pintad  papar  covors  ara  fllmad 
baginning  with  tha  front  covar  and  anding  on 
tha  last  paga  with  a  printad  or  illustratad  impraa- 
sion,  or  tho  back  covar  whan  appropriata.  All 
othar  original  copioa  ara  filmad  baginning  on  tha 
first  paga  wKh  a  printad  or  Illustratad  impraa- 
sion,  and  anding  on  tha  last  paga  with  a  printad 
or  illuatratad  imprassion. 


Tha  last  rocordad  frama  on  aach  microfiche 
shall  contain  tha  symbol  — » (moaning  "CON- 
TINUED"), or  tha  symbol  ▼  (moaning  "END"). 
whichavar  applias. 

Maps,  platas.  charts,  ate.  may  ba  filmad  at 
diffarant  raduction  ratios.  Thoso  too  larga  to  bo 
ontiraly  includad  in  ono  axposura  ara  filmad 
baginning  in  tha  uppar  laft  hand  cornor.  loft  to 
right  and  top  to  boRom.  as  many  framas  as 
raquirad.  Tha  following  diagrams  illustrata  tha 
mathod: 


Laa  axamplairas  originaux  dont  la  couvartura  an 
papiar  aat  imprimAa  sont  filmOs  an  commancant 
par  la  pramiar  plat  at  an  tarminant  soit  par  la 
darnlAra  paga  qui  compona  una  amprainta 
d'impraasion  ou  d'illustration,  soit  par  la  sacond 
plat,  salon  lo  cas.  Tous  las  autras  axamplairas 
originaux  sont  filmis  an  commandant  par  la 
pramiOra  paga  qui  comporta  una  amprainta 
d'impraasion  ou  d'illustration  at  an  tarminant  par 
la  darniira  paga  qui  co'  iporta  una  taila 
amprainta. 

Un  daa  symbolas  suivants  spparaltra  sur  la 
darni*ra  imaga  da  chaqua  microfiche,  salon  la 
cas:  la  symbols  -^  signifia  "A  SUIVRE".  la 
symbolo  ▼  signifia  "FIN  ". 

Las  cartas,  planchas.  tablaaux.  ate.  pauvant  itra 
film*s  A  das  taux  da  rMuction  diff Grants. 
Lorsqua  la  document  ast  trap  grand  pour  *tra 
raproduit  an  un  saul  clich*.  il  ast  film*  A  partir 
da  I'angia  supiriaur  gaucha.  da  gaucha  A  droita, 
at  da  haut  an  bas.  an  pranant  la  nombra 
d'imagaa  n^cassaira.  Las  diagrammas  suivants 
illustrant  la  m«thoda. 


1 

2 

3 

1 

2 

3 

4 

5 

6 

hrr^r^ 


II." 


\^ 


'  THE  NATURE  OF  A  SUPPOSED  VARIATION  IN 
THE  SOLAR  ROTATION  IN  1915 


"a 


KM  I'll   I      DiirUN 


[ 


JA\  1  -^ 


Kr;.tint,'.l    i    "    P•'^    >"     ' 

I  III     \~iK-.ii'ii.-l'   M   J"'  ^■■^'     ^'  '■'" 


1,   ,;l.l''..!l    It. 'in 
\l.\    III      \.. 


,  (  1,  lot  I't     I.il  ■ 


s^Sii^^m^:r,^sm^^^^ijmm'^^^^^^ 


,'■  f: 


■ 

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« 

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r.      '  -.•    ' 

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-,,,  -^ 


v^;:"v 


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lUK  x.vrrKK  OF  A  SI  iMM)si:i)  \ AKi.viniN  i\  im: 

SOLAR  KolAlloN    IN    i.n^ 

U\    KM.I'II   I,    IM  I  IKS 

In  ;i  l)riif  note'  ividtiuc  \va>  |)r(>inti(l  wliiili  imlit.itdl  ili  it  the 
C(inilu>ion'  drawn  hy  Mr.  II.  II.  iMa>kilt  'tliat  the  >un.  ■hiriiiu 
Ihf  suninu-r  i>l  11)15.  undrrwint  a  ivilic  variation  in  it~  rotation 
rate  of  0.15  km  ....  loinpktol  in  al>out  .1  month,"  \\a>  not 
jii.'^tififd,  ant!  that  this  variation  in  ^luctro-ioiiic  nua^urcmcnt^ 
of  thi-  vi'loiitv  of  rotation  of  the  svm's  e<|uatoriai  linil»  mij-lu  Ik- 
due  to  ihan>;e>  in  terrestrial  ha/e.  Mr  IMa>ketl  ha>  critiei/ed' 
this  e.\j)lanation  without  testing;  my  su),'^;e>tion  tliat  renua-ure 
ments  or  an  analvsis  of  old  measurement>  sliould  >how  ion  anount 
of  he  presence  of  blended  sjiei  truni  of  ha/e  in  the  ol)r.er\  ation■^  in 
(jue>tion)  smaller  di-plaeement>  of  weak  than  of  ^troni;  >i)eitrvim 
lines,  partieularl)  on  the  day-  when  the  lowe-t  value-  of  the  rate 
of  rotation  were  obtained,  i.e..  on  the  day-  01  ^jreate-t  ha/ine-s. 
In  what  follows  new  e\  idinee  eonl'irmini;  this  e\i)laiiation  i-  i^ivi  11 
alon^  with  an  eku  illation  of  the  eritiu-m-.  whieh  .ire  rel'e  d  to 
hy  their  numlxrs. 

1.  I'rom  a  lonsiderahU  numiier  of  oh-ervations  with  respei  t  to 
ha/e  Mr.  I'laskett  selected  three  of  my  oh-ervation-.  implyiui;  that 
these  were  all  I  had  made,  lie  plaee-  the-e  oh-ervation-  of 
obviously  ehanj;ed  eondition-  be-ide  hi>  mea-ureimnts  of  i)lates 
made  >ome  hours  pre\'ou,-ly,  implyinj;  in  the  wonls  "low"  and 
"high"  that  the  ha/e  e.xplanation  has  been  eontradii  ted.  tlui-: 

During  llic  iHritiil  umler  niri-iiliratioii,  ii.iiiuly  Jiiiu'  ji  lo  .\u(;ii-t  ifi, 
beLury  nuide  three  ciitrie-  in  the  iil)serv.ilii)ii  Imuk  uilli  relirciue  In  li.i/e; 

June  -M,  "HriKht" I'"  1   'H  1  (l<>«^ 

July  II,  "Wry  hazy" I'     1   '(7  ^  'hinh) 

.\uKiist  i().  ■"Hrinht,  some  walirva|«)r  ha/i" l'      i   077  (hiK'h) 

'  A^lrofiliysii.il  Jiuiriuil.  44,  i<iS.  nd'i. 

'Ihitl.^i.  1511.  icji''.  'lh:,1..4S,  I4.J,  lui;. 

")5 


U^}  KM  I'll  /,.   1)1 1  '  AT 

Iii>t('a<l  1)1°  tlii>  he  >l)(iiil<l  luuc  aili^jitril  tlic  lo^iial  priunlurc 
of  juxlaixoiiii;  a>  follows  hi>  own  ol)MT\ation--  with  nfiTcmc  to 
lia/i'  and  the  ri>|H'ttivi'  \aiiiis  of  liu-  viloiity  of  rotation,  inulin); 
in  aironlanci-  with  tlu'  lia/.f  t-xplanation  that  low  \aluis  of  the 
inrasurrnuiits  of  >olar  rotation  arc  as>oi  iatcd  with  ha/c  and  hi^;htr 
vaiiu-s  with  "no  ha/r."  thu>: 

\    in  kn(  i-^T  *#■( 

Juiif  .'J,  ■■  H.  <  4,  A  lilllr  li;i/i  mar  >un" i  S46 

July     4.  "  H.  t  4.  Ilazf" 1  .Hijs 

July  :o.  "  H,  4.  No  ha/c  "  .•  ojO 

July  .',(.  ■■  \\.  4  5.  I'i)>ili\tly  iid  lia/o" .•  cx)< 

.\uKu>l  1(1, '•  |{.  4,  I'ratliially  lillli' i>r  no  lia/c" 1  cj;; 

That  hi-  comiiuiti'd  ;in  error  in  sfltin;.'  hi>  mrasuri's  of  rotation 
ovrr  against  my  ri'iorii>  of  rlianncd  londitions  inadi-  latir  in  tlu- 
day  is  a|»|)arfnt  from  a  con'>i<li'ration  of  iahk'  I,  whtrc  his  and  my 
moasuriimnts  for  tbrsc  thrrt'  scli-itod  days  an-  ass(H'i;'.ti'd  with 
thi'ir  n'sjuTtivi-  riiords  of  l)rij;htni'ss,  the  ol)srr\ations  Ixinj;  in 
harmony  with  tlu'  iia/i'  i'.\i>lanation. 

IMtl.I,  1 


i 

I'l  v-kj  rr 

XnU  H\ 

l»\n 

Tiirc 

Hrin(ilni-»s 

km 

1  tnu- 

HrichI  t)t'-> 

A 

Km 

Junt-  :i 
JuU    1 1 

^  i^     S  00 

1 

I  tjll 

10 

1  ■•<   10 

i.H 

Hriht 

''oO 

1    007 

7  00     7   ly 

I,    'Ihi-n  h.i/cil  u|t" 

I  u:=; 

'J 

.'0    10 

i^H 

\tr\  ha/v.  tirru".  .linui- 

'      ^•y.iO 

I    iM 

I  r 

\:  II 

1>J 

Hrik'tit'  r.  -.till  hiizv 

s'  00 

I    So^ 

Augu-t  !'• 

S     to    1  I     I'J 

4.  ■pruttHallv  lilllf 

I    U77 

1  2 

47    l-i 

M 

liri(.'ht .  Htime  vKalff- 

i 

ur  ntr  ha/.t' 

i 

\aiKrr  hii/f 

5tKX3 

I  yig 

It  is  sinnilkant  that  on  Jmu'  ;i.  when  lu'  ohtainrd  ;;  valui-  of 
1 .1)1 1  kill  piTsw.  oiu'of  till-  low  vahu's  in  thr"cyciic  variati  ins" 
1  ohtaini'd  a  kw  hours  aftiTward  j.007  km  [kt  si'i.,  a  valuf  about 
i-ijual  to  thi-  maximum  values  in  the  supjxiscd  variation.  I'mh- 
ahly  the  record  "Hrifjht"  indicated  a  {greater  hrij^htness  than 
"H.  4"  of  that  date. 

On  account  of  the  haze  which  developed  after  I'laskett's  plates 
were  taken  on  July  1 1  and  which  remained  throuf^hout  my  observa- 
tions these  l.ilttr  (14  ])lates  at  X  5000  and  7  at  X  5600'  yield 
decidedlv  lower  values  than  his. 


(»V   so/.  lA'  Hi>l  \l  l<>\   /  V    ;.;;,- 


M)7 


(In  Annual  I'l,  prill). il>l\  mi  .nunint  nl  llic  |iri>cni<  mI  "^ninr 
watiT  vapor  ha/c,"  my  i>l>-.ir\alinii>  •■•  plati>  at  X  ;'kx:i'  yiclil  a 
valiU'  .'  piT  (tilt  lower  than  i\i>. 

All  tluM-  riMill^  are  aMrihaMc  to  ilitTtnni  dc^'nt-  oi  ha/iiir-> 
in  aiTorilaiur  with  the  n.onl^.  rurlhrr  .l.laiU  art  n'wiu  in 
lahlr  II. 

kinanlin^;  his  rrconi  ot  l)ri«hliu->  Mr.  IMa>kiti  ^lati»; 

5  ri'prtsitils  ;i  vrry  lirilliaiit  'lay     rare  in  (>ll.i«a. 
•l  ripris«'nt>  a  liri^tit  ila>     imrmal  nliv  r\ii)i;  "I'.iilur 
(  rfpriM'iil:.  a  il.iy  -li^rlilly  lia<iy. 

IhfM'  statements  are  >ell  on.  taili  'ory.  presuniint;  that    >iu  h 
.lil'lVrent  (le;;ree^  of  hri^h'    •  --  pi>-tulaie  ilil'   rent  «le>;rees  of  ha/i 

'ime  our  reioriK  of 

M'  a     ount  was  kejit 

>urini;  tlie  iia^t    two 

he  li"        II  the  spei 

K  ;(KX3     'lii'  oriler, 

;roj,'rapli.     -■lit 

■»ii>i.      r>uaily 

l'lale>  taken  oti 

i-  a  nii^re.elinj;  oi 

-ki  ti  were  taki  n 


ness.     On  no  (la\-  was  h     e  aloeii'        \'  tt 
ohservinj;  eomlitions  \'    .<  ineompi  ii  in 
of  liie  strentith  of  the  >i)eetrum  oi   lia/i 
years  on  no  ilay  has  it  heen  iin|)o-.>il>''    -. 
trum  from  ha/e  just  out>iile  the  ^.ilar    inv 
jm     auto  lollimatinK     l^im-Siii'l     '^\ 
o.o;  mm,  fed  l>y  the  4;  em  eoneave  mirror 
the  line>  are  distinetly  vi-ihie.     A^.iin  iu-  - 
(lays  ha/.ier  than  ,^.5  were  not  mea-ured. 
the  record,  as  14  of  the  1 1 1  plates  mea>ured 
at  recorded  hri^ihtness  ••  ;. " 

IMaskett  also  assert. ■-:   "'Ihe  record,  if  it  n  vtl 

that  in  j;eneral  hijih  valui'>  were  ohtained  "ii  \. 
values    on    hri^jhter    days,    in    diri'ct    contraditti 
statement." 

That    this  miulusion  i^  faliaiious  is  -een  Irm 
(omplete  >ummary  of  hi>  ohMTvation-  ithou;,'h  it  i 
have  the  adnii^Mon  that   tliere  were  ha/,y   day>i.      I 
ments  of  the  1  1  1  plates  may  he  grouped  with  re>,'ard  1 
"ahove  normal,"  "normal,"  and  "iHiow  normal,"  u-i' 
delinition  of  a  normal  dav  ^ivi'n  above: 


-    .   .  .    iow 
'>el  ur\  - 


K)  plates.  It.  "  ^"  aiiil  " .\   5,"  me.iii  viloiity 
50  plates,  B.  "4.  '  i.e.,   ■norm.il."  iiu-.iii  velmily 
4-'  plates.  H.  "  i  4"  ami  "  i,"  nu-.iii  vtloiity.     . 


iqK 


AM/./7/  I:    PeH  KY 


It  may  \h-  iiotid  that  4.'  of  llu'  1 1 1  platts  \s\u-  madi  1  lay  ,)|' 
l)ri),'htnf»  hi  low  'nomial."  i.e.,  on  days  of  ha/i-  prisunial)l\  .../ovf 
normal  Also  4^  of  ilu'  in  iilalc^  wirr  taki-n  at  l>ri^;ht noses 
riTonlcd  as  "4  5"  ami  's  4-  terms  >o  vamu-  as  to  indiiatr  tiilu-r 
unccriainty  in  tin-  rstimati-s  of  hrinhtmss  or  varying  tU-gnrs  of 
ha/imss.  Winn  su(  h  una-rtainty  in  tin-  riiords  ixisls.  tin-  supiwirt 
wliiili  tilt  nummary  j;ivis  to  tlu-  ha/i-  txplanation  is  as  sati>fa(toiy 
as  can  hi-  i-xpccted. 

'Ihr  K)  plates  of  the  first  Kfup  includi  15  at  "H.  4  5,"  moan 
velocity  i  .()!S()kni  per  sec,  and  4  at  "  H,  5,"  mean  velocity  r.oiijkm 
per  sec.  The  accuracy  of  this  hifjh  record  of  hri>;htness  (the  only 
one  of  "H.  5")  may  l)e  questioned,  as  it  was  the  first  made  (on 
July  ())  l>y  I'la^ki  It  after  the  three  mirrors  of  the  coelostat  telescope 
had  been  freshly  plated  (July  7),  and  it  is  prohalde  that  the  much 
hri^hter  ima^c  of  the  sun  produced  as  a  conseijuence  jjave  the 
ohstrver  an  exai;f;erated  impression  of  the  clearness  of  the  sky. 
If  the  day  were  in  nality  ha/y,  then  the  i)lat' .  should  satisfy  the 
criterion  for  blended  sju-ctrum  of  ha/e.  I  have  measured  the  4 
l)lates  and  find  a  dilTerenceof  0.054  km  per  sec.  hetveen  the  values 
of  the  \elocity  of  rotation  cleduced  from  nrou])s  of  weak  and  of 
stront;  .■spectrum  lines  a  dilTerence  which  may  be  interprete<l  as 
indicating  the  presence  of  a  considerable  decree  of  haziness  (see 
Table  II).  Hence  it  i>  reasonable  to  sup])ose  that  record  "H,  5" 
for  the  bri>;htness  duriiif?  his  observations  on  July  0  is  too  hi^h 
relative  to  the  other  ncords  and  for  the  lause  indicated. 

I'rom  the  foreKoiiiL  summary  of  his  records  and  measurements 
it  is  (|uite  evident  that  the  following  statement  which  appears  in 
his  original  paper  \\i.  147)  is  not  justified:  "Observations  were 
never  made  exce|)t  on  days  that  were  free  from  ha/,e." 

2.  Mr.  riaskett  states  in  his  note:  "DeLury  bases  his  di.scus- 
.sion  on  plates  made  on  two  dates,  June  24  and  July  20,  which  are 
described  as  'Ha/.y'  and  "Hright,"  apparently  from  memory, 
as  it  is  not  so  recorded  in  the  observation  book." 

On  June  24  he  recorded  "'H,  .V4,  ;i  little  hii/.e  near  sun,"  at 
7:40.\.M.  before  his  two  observations,  and  "B,  3-4"  at  o:io.\.M. 
after  these  ob.servations.  Memory  need  not  be  appealed  to  for  the 
description  "Ha/y"  for  these  conditions.     On  July  20  he  recorded 


i 


O.V  .NO/  lA'  KnI  \l  lii\    /  V    /u;-; 


UXI 


I 


■■Hri^'lil    141 "    tli.-fc    linio    lor   inlirv.ilN   ^:.<;  j-.oS.   S:o^  •*<■.  ."l 
and  .S:^S  S:.}^  \  m.;    aUo,    "  \i>   li;i/c  "      I   iiliNir\t'<l    'rurn   >>    -.\ 
10:  1 1  AM,  ,illiiwii>n  tlu-^f  rtiunl--  In  -IawA  until  .1  » li.m^;r  ok  urn. i 
ju>t  al'tiT  llii>.  wluM  I  rrmnUd  llril  il  •  .loinlrtl  up  "     Hi  luc  ilic 
linii  ■'Hritilit"  i>  ju-tilui!    "4"  rtpriMniint:.  .uionliim  to  him,  a 
"l)ri>;lit  flaw  normal  olxcrxiii^;  we;  t her." 

In  till'  lollowinn  two  ini>^l,itt  nicnt^  arc  m.ulf;  'iin  June  .<4 
Di'Lury-  plalis  \v»t»'  takiii  lhrou>;h  cIoikIs  whos,-  pn^mff  lir 
notis  in  till-  ol)strvalion  luiok.  wlu-rras  the  writir'^  plat"  -.  tximNiil 
oariiiT,  \v(Tf  takin  with  a  rUr  •  sky."  On  this  dali-  my  mii^iiml 
piatis  at  X4-'io  wiTi-  takrn  at  10:  iS  10:54  \.m  .  ami  ihoii'^'h  I 
niadf  olisi'ivations  up  to  noon  I  did  not  ntord  "iloudid  up  '  until 
afttrnoon.  Ahsohitily  no  miiitioii  of  rloiids  was  made  l)tlor( 
noon,  so  that  the  siatinu-nt  that  m\'  "plati-s  wi'i>  'aki'n  tlirou;;h 
c'it)uds"  is  not  corri'ct.  Also,  as  shown  al)o\c,  on  June  -'4  he 
dfscrilK'<i  thf  ronditions  as  "a  little  ha/o  mar  thr  sun  '  and  'It, 
,^  4."  so  that  the  term  "clear  sky"  l>y  iiisowu  dei'mition  i   inoim  t. 

In  addition  to  tlie  dirert  statement  ol"  the  re'  r  -  as  to  the 
relative  hrightness  of  the  two -,elet  ted  dates,  June  .  ,,i  I  Jul  :o. 
rem.  asurementsof  my  plalesat  X  i-' ;o  and  mea-urenun  •  liy  n  If 
of  hi>  jilates  at  X  ,>i)00  yield  further  eontirmation  of  mv  e\])lan,ition, 
for  on  June  .'4  the  dilYerenees  ln-tween  jjroups  of  measurements  of 
weak  and  strong  lines  are  j;reater  than  for  tlie  same  lines  on  Julv  :o. 
pointing;  to  a  greater  dej;ri-e  of  ha/ine-s  on  llie  former  dale  i-<ee 
Table  11). 

lAitii;  II 


I  till.- 

linir 

Hriirhtm-N 

No    nt 
I'l.it,- 

A 

\h   ..i 

Mr.i.i 

ktn 

\..    . 
I.lti.' 

■«ttv 

•  itV     Ml 

km 

Ihiftr 

fin  1-  III 

if  r  M'i 

\<*t  ^i 

illy 

J 11  IK-  J\ 

M   1 7     u   10 
la   iS    10    K\ 

i    I 

2 

1 1 

4     7 

1     7'Ki 

I    71  i 

\ 

1 1 

1    ■<5-, 

I  "';7 

0   ogs 

^  1  n 

Julv     ., 

Hoi     S ,  .■  J 

;    nn'riir"  rr|l.i 

I.-.! 

\ 

;iioo 

1 1 

1     ,^.^> 

i 

1 1 

I  *ji.' 

r,     i:;i 

July  1 1 

10    J  S    10    s"* 

\rr\  h.i/\ 

•  I 

st><X) 

1 1 

1     7''; 

1 1 

I    •<>: 

J     O."*  1 

11:  17    II     IQ 

Hri/htcr.  >iitl  h. 

:i;:v 

7 

(f-K) 

\ 

T      1, 

I    7'^i 

^ 

>     1    ■*:'■ 

'J    -JXK 

July  20 

6 ; J  I       So? 
Q    >  I     t'      II 

1.  im  h.uf 

I 

1 1 

\    7 

I    -i-H 

i 

1 1 

i   ■-.'.■ 

•J    .it 

Aue  I'' 

i.v  J7   i:   w 

h.izc 

.il**»r 

• 

;'KX) 

I 

0     ( 

1    ')     J 

<. 

I     I    •i','1 

0    xyj 

Tahle  II  gi\es  in  di-tail  the  new  measurements  disc  u>-t'd  aliove. 
'I"hey  are  all  in  harmony  with  [he  ha/e  (Xplaiiation.     (  M\   14  plates 


20O 


RM.I'II  /•:.   IhlARY 


at  X  5<)00,  July  ii,  yifldi'd  a  vi^Iocity  of  — o.ooO  km  jK-r  sec.  for 
tlio  nu-aiis  of  4  atmospheric  lim-s,  showing  that  little  error  need  l)e 
feared  when  the  proper  precautions  in  focusinfi  the  plate  and  in 
illuminatiii),'  the  j;ratinj{  evenly  are  taken.) 

Ki'j^ardin^  the  jxissihility  of  errors  of  measurement  in  the  results 
j;i\en  in  my  note  Mr.  Plaskett  says:  "The  dilViculties  of  measure- 
ment of  hro.hl  lines  increase  the  errors  and  chances  of  preposses- 
sions, espicially  with  an  observer  whose  last  published  measures 
show  a  probable  error  for  even  well-detined  lines  of  o.c.km,  i.e., 
of  the  same  order  as  the  dilTerences  measured." 

'I'here  are  no  "chances  of  prepossessions,"  for  in  all  of  my 
spectroscopic  measurements  there  is  used  a  movable  mask,"  which, 
l)y  permittinj;  only  one  strij)  of  spectrum  to  be  seen  at  a  time,  keeps 
hidden  not  only  the  maj^nitude  but  also  the  direction  of  displace- 
ment of  the  spectrum  lints  beinjj  measured. 

In  the  series  referred  to  the  averaj^e  probable  error  was  0.052  km 
per  sec.  (not  0.06),  and  in  tlii:^  \<ry  series  numerous  reiieated 
measures  of  a  certain  jilate  have  previi  jsly  shown  that  about  half 
of  this  "probable  error  of  a  sin,L;le  line"  is  due  to  actual  dilTerence- 
for  different  lines  on  the  plate.  Also  the  ])lates  used  in  the 
series  referred  to  are  of  coarser  ^XAin  and  the  defmition  of  the 
lines  is  poorer  than  for  the  j)lates  at  X  A-?i<^-  referred  to  in  my 
note. 

In  Table  II  are  );iven  the  means  of  si.\  measurements  of  the 
latter  plates  1X42,^0.  June  24  and  July  20),  including  the  single 
measures  reported  in  my  note  three  violet  right  and  three  violet 
lift.  The  former  single  measure  dilTers  from  these  means  by  o.ooj 
and  0.01,^  km  per  sec.  for  the  Ke  lines,  and  o.oO^  and  0.021  km 
per  sec.  for  the  broad  ('a  line;  or.  expressed  in  millimeters,  these 
(juantities  are  o.ooor,  0.0005,  0.0024,  'Hi<l  0.0008.  The  differ- 
ences in  velocity  between  the  ("a  and  the  Fe  lines,  namely,  0.14,^ 
and  0.022  km  per  sec,  point  to  an  even  greater  elTect  of  blended 
si)ectrum  of  ha/e  than  was  supposed  from  the  dilTerences  0.082 
and  0.014  km  per  sec.  given  in  the  previous  note. 

It  bears  strictly  on  the  whole  (juestion  to  comi)are  these  dilTi  r- 
ences,  based  on  measures  of  a  single  l)road  line,  with  .Mr  Plaskett  s 

'  Jounuil  of  I  III  Hoyjl  Ailroiuwiiiul  Smiily  of  diiitiJii,  5,  405,  igii. 


(».V  .SOI.AK  KOI  Alius   /V    /^/i 

t'.vo-way  nieasuronii'nts  of  '/:r  M>lar  liiu'>  un  1 1 1  platen,  whii  li  wluti 
ri'pratfd  yidtli-d  an  aviTajjc  (lii'l'irri\<  f  lutwciii  llif  iman>  m 
0.055  km  I"'''  ^^'*''  "'  wlii'li  (lit"UT(iui>  iS  I'Xticdid  0.100  km  |)ii 
sec.  and  ()  havr  a  mean  of  o.  1  5J  km  piT  sit.  of  the  ^ann-  ma'^Miiludt 
as  till-  ■"ivclii-  variation  of  o.  15  km  per  sci."' 

'I'hf  dilTcrcnci's  diTivi-<l  from  llu-  nuan-.  of  tiic  luw  nua-'Urc 
ments  of  the  X  42.^0  plates  of  June  .'4  and  July  jo  clTiTtivtly  .iimul 
the  followinf;  arjjument  (evin  if  we  o\crlook  the  fail  tliat  it  i^ 
fallacious  to  arjjue  as  he  has  done  from  m\  mea>uremenl>'  al  X  5:00 
to  those  of  other  lines  at  X  4J,^o  without  ])re\iou>ly  comparing  the 
extent  of  the  chanfje  in  character  of  the  two  sets  of  lino  in  pa^in;; 
from  the  center  of  the  solar  disk  to  the  iimhs): 

The  measures  show  evideiue,  adDnliiij;  to  ihe  iritirion  oi  v.iryiii^:  viloi  ilv 
for  (iilTerenl  line  intensity,  of  about  S  [kt  cent  haze.      I'his.  cm  his  ou  n  h\  |iiii  h 
esis,  should  prixluii'  ahout  an  S  [ht  cent  (lilTtrciuc  in  velocity  on  tin-  two 
dales.     The  (lilTereme  in  mean  veltHity  is  ailually   u  |ht  unl,   h.iviii>r  a 
4  |HT  cent  change  in  velocity  to  lie  accounted  lor. 

,v  The  arguments  as  to  the  dirfereiices  in  vahu-  of  the  rotation 
for  low  sun  and  sii<;htly  hij^her  sun  are  hasi'd  on  "■  mi-a^jer  and  iiii  on 
elusive"  data,  and  the  (juantitiis  derive<l  art'  so  \ery  small  'a  few 
thousandths  of  a  km  per  sec.i  that  they  are  without  nieanin^j  when 
such  large  errors  of  measurement  are  present.  .\  \iry  iar>;e  ><ries 
of  ol)-ervations  of  the  solar  rotation  from  early  morninjj  to  late 
afternoon  would  jjive  evidence  as  to  the  daily  development  (usually 
increasing  at  Ottawa)  of  ha/.e  durinjj  that  day.  and  if  many  days 
were  likewise  considered  a  valuahle  statement  tould  he  matie  as  to 
the  daily  develojniient  of  haze  at  the  locality  of  the  ol)>ervation>. 
No  such  measurements  couhl  pos-ihly  ca>t  douht  on  the  ha/e 
explanation  unless  at  the  same  time  contradictory  e\  ideiK  r  of 
the  chanj;es  in  haze  were  obtained  by  other  reliable  means. 

It  may  be  said,  in  conclusion,  that  the  facts  presented  above 
make  the  claim  that  the  sun"s  rate  of  rotation  varied  in  i()i5  seem 
very  unreasonable.  All  others  who  have  made  spectroMojiii 
investigations  of  the  solar  rotation  have  found  varieiv  in  thiir 
measures",  and  some  have  suggested  the  possibility  that  the  rate 

'  .{ilrop/iy^iiiil  Joiiriitil,  44,  1S4,  loi'i. 


202 


KM. I'll  /•:.  Dh.l.l  RY 


varied.  I'K--  ^-  ■'^-  Vouii};,'  Halm.'  Kvorshetl  and  Royds',  St.  John, 
Adams,  and  Wan-.'  However,  Halm'.s  low  values  in  iqo2  iqo.^  can 
i)e  readily  accounted  for  hy  the  haziness  produced  by  the  volcanoes 
in  the  West  Indies  in  1902.  which  caused  a  marked  lessening  in  the 
values  of  solar  radiaticm.  The  low  values  obtained  in  1912- 1913  by 
livershed  and  Royds  may  have  been  due  to  the  Katmai  eruption 
in  June  1912,  which  also  caused  a  great  lessening  in  the  measures 
of  solar  radiation.  The  low  values  of  rotation  obtained  at  Mount 
Wilson  and  ( )ttawa  in  i  c)  1 5  also  seem  to  synchronize  with  low  values 
of  radiati(m.  i.e.,  it  may  be  presumed,  with  high  values  of  haziness. 
Ajxirt  trom  haze  \arious  instrumental  and  physical  causes  produce 
variations  in  the  measurements  of  solar  rotatiim.  When  the  effects 
of  all  known  causes  (haze,  local  convections  in  the  sun,  errors  of 
measurement,  etc.)^  are  eliminated  or  accounted  for,  it  probably 
will  be  ])ossible  to  assert  that  the  rate  of  the  sun"s  rotation  does 
not  ap]ireciably  vary. 

The  foregoing  may  be  summarized  briefly  as  follows: 

1.  The  arguments  which  Mr.  H.  H.  Plaskett  advances  (in  his 
note  critic!  '  my  e.\i)lanation  of  his  observations  of  a  supposed 
"cvclic  variation"  in  the  sun's  rate  of  rotation  in  19 1.^,  iis  due  to 
variations  in  terrestrial  haze)  are  based  on  fallacious  use,  or  inaccu- 
rate statement,  of  the  records  and  the  measurements. 

2.  A  synopsis  of  Mr.  Plaskett's  record  of  observations  and 
measurements  of  the  solar  rotation  supports  the  conclusion  that 
in  general  high  values  of  the  rotation  were  obtained  during  brighter 
conditions  and  low  values  during  hazier  ccmditions. 

V  Measurements  of  Mr.  Plaskelt's  plates,  as  well  as  of  mine, 
satisfy  the  criterion  of  blended  s])ectrum  of  haze  in  agreement  with 
the  record  of  observational  conditions. 

4.  'l"he  knoxi'n  terrestrial  sources  of  blended  spectrum  offer  a 
reasonalile  e.\i)lanation  of  the  supposed  variation  in  rotation,  so 

'  ///('  Sun  (!■'*•'*-'.  P-  'oo- 

'  TriiiisiUlioiis  of  I  lie  Koyal  Sociily  of  Edhibiirgh.  41,  .Si).  1004;  anil  .1  ^Iroiiomisilif 
Xtiihriililiii,  173,  2H7,  iQofj. 

>  Mo,,, Illy  .Xoliics,  ij,  554,  KMi- 

*Pol>iiliir  .l>lroiion}y,  13,  041,  U)I5- 

5  hil.ury,  Aslropliysicil  Journal.  44,  17.S,  iqiO. 


O.V  Sor.AK  KOIMIOX   l\    /y/? 


203 


that  it  i>  unnuccssary  to  employ  the  liyf>ntliiii<,il  ilcmriit  ol  nn 
L'xphination,  which  sup))()si's  an  inti-qilant'tary  or  solar  >ovirit.'  of 
blended  spectrum. 

5.  At  i)resent  there  is  no  sound  reaxm  lor  l)elitvinj;  that  the 
rate  of  the  sun's  rotation  is  variable. 

I  wish  here  to  thank  the  director.  Dr.  Klot/.,  lor  his  approval 
of  the  publication  of  this  note. 


Soi.AR  I'liYsu  s  Division 

I)i)MlNfOX  OllSKRVATDkY,  OTTAWA 

May  KjiS 


